F O R M 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
A MONOCOQUE, ELECTRO COATED, MODULAR BUS BODY STRUCTURE AND METHOD FOR JOINING MODULES TOGETHER
2. APPLICANT(S)
(a) NAME FORCE MOTORS LIMITED
(b) NATIONALITY INDIAN Company
(c) ADDRESS MUMBAI-PUNE ROAD,
AKURDI,
PUNE-411 035, MAHARASHTRA, INDIA
COMPLETE (√)
The following specification particularly describes the invention and
the manner in which it is to be performed
4. DESCRIPTION (Description shall start from next page)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble – “I/We claim” on separate
page)
6. DATE AND SIGNATURE ( to be given on the last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on the separate page)
Note:
* Repeat boxes in case of more than one entry
* To be signed by the applicant(s)or the authorized registered patent agent
* Name of the applicant should be given in full, family name in the beginning
* Complete address of the applicant should be given stating with postal index no. / code, state and country
* Strike out the column which is/are not applicable

PREAMBLE TO THE DESCRIPTION:
The following specification, particularly, describes the invention and the manner in which it is to be performed:
The present invention relates to a light weight, monocoque modular bus structure individually electrocoated and, more particularly, it relates to systems & method of joining pre- electrocoated bus structure modules together. This invention enables manufacturing in a process friendly manner. Apart from this, the assemblies become light weight & cost effective. The size and cost of electro coating tank can be kept low.
PRIOR ART:
1) Conventional bus bodies are built with Body over Ladder Frame Chassis approach. These bus structures are made using thick tubular steel sections, which are joined together using MIG welding to form a shell of a bus. As these tubes are closed sections, many brackets are required for the fitment of other interior & exterior bus body parts. As these structures are large, single shell, it becomes difficult to provide appropriate anti-corrosion treatment to the structure and weldments. The body construction approach results in a heavy, overweight shell. Overall, this adversely affects performance & fuel efficiency of a bus.
2) Monocoque bus body structure are welded as a full bus shell and then electro coated as full structure. This requires huge and expensive welding fixture as well as a very large tank capacity and expensive electrocoating plant.

OBJECT OF THE INVENTION:
The main object of the invention is to build a monocoque bus body structure in modules, which is efficient, easy to install and becomes integral, after assembling the modules together.
The other object of the invention is to provide a bus body structure which is protected fully with anti-corrosion treatment for a much improved service life.
Another object of the invention is to provide a bus body structure that is significantly lighter than that are made using conventional bus structure building approach.
Another object of the invention is to provide a cost effective bus body structure.
Another object of the invention is to provide a solution for making different lengths of bus bodies having different seating capacities using common modules.
Another object of the invention is to provide better ride comfort due to the increased stiffness of the structure.
Another object of the invention is Commonisation of structural parts which are produced though stamping process for reducing investment and cost of parts.
SUMMARY OF THE INVENTION:
To achieve aforesaid objects, the present invention provides a solution comprising 2 modules of the body structure which form a monocoque after the modules are individually electro-coated and attached together. The modules are connected together by means of an innovative concept. The above monocoque forms a robust, integral bus

body structure which has superior corrosion resistance & lighter in weight. There is a new, unique process for assembling the modules together.
BRIEF DESCRIPTION OF THE DRAWINGS:
Fig.1 : is a perspective view of front and rear bulk heads.
Fig.2 : is a perspective view of front and rear bulkheads bolted together before they
are welded to front and rear modules respectively of the bus body. Fig.3 : is a typical section of the front & rear bulk heads of the monocoque modules. Fig.4 : is a typical section where bolts are used to pre assemble and match the front
and Rear bulkheads before they are welded to their respective modules of the
monocoque. Fig.5 : is a typical construction of front and rear bulkheads. Fig.6 : is an exploded view of the bulk heads. Fig.7 : is the perspective view of the front and rear chassis modules Fig.8 : is the perspective view of the chassis (Shown as when the modules are
connected). Fig.9 : is a perspective view of the details of the joint of chassis on front and rear
modules of the monocoque. Fig.10 : is a perspective view of the front and rear modules of the monocoque cubed
and matched prior to the CED coat. Fig.11 : is a perspective view of the front and rear modules of the monocoque
separated after cubing and matching prior to the CED coat. The additional
stainless steel reinforcement to be welded at the chassis connection is also
shown. Fig.12 : is a perspective view of bus body structure, joined together after CED coat. Fig. 13 : shows the use of common parts at multiple locations on the structure. Fig. 14 : is a list of common parts described in fig.13

Fig.15 : shows the welding on the stainless steel bulk heads of front and rear
modules. Please refer to section C-C in Fig. 12 Fig.16 : shows the perspective view of the complete bus.
DETAILED DESCRIPTION OF THE INVENTION:
1) Traditionally, bus body structures have been built using standard rolled steel
sections like rectangular or square tubes, angles and channels. These sections are
made from hot rolled steel sheets. Co2 MIG welding is employed for joining
these sections. Such structures, after the attachment of skin panels, are painted in
a conventional manner, primarily, due to the reason that the size of the structure
cannot be accommodated in normally available pretreatment tanks .Such a body
shell is subsequently bolted to a ladder frame chassis made out of heavy rolled
sections. Sometimes, a combination of welding and bolting is used. This
approach and process of bus body making has following major disadvantages.
1. Heavier body structure which results in less pay load and low fuel efficiency of the vehicle.
2. Laborious manufacturing process due to extensive use of Co2 welding.
3. Reduced overall stiffness of the structure which puts the safety of passengers at risk.
4. Less productivity and reduced dimensional compliance and repeatability.
5. Very less corrosion protection due to the inferior paint process.
6. Heavily relies on manual skill for fabrication and finishing.
2) Monocoque bus structures produced elsewhere are welded in huge fixtures as
complete shell and parts cannot be welded after electro coating. Full shells are
electro coated in very large plants where each tank has to accommodate full bus
shell.

The present invention addresses above pitfalls in conventional design.
A monocoque shell is produced from stamped cold rolled steel parts and sub assemblies which are joined together by spot welding. The stamped parts which guarantee high degree of dimensional consistency are standardized at many locations to reduce the parts count .Robotic Spot welding cell with electro pneumatic fixture is employed which ensures highest level of stiffness and accuracy of the assemblies and sub assemblies . The body shell is made out of two modules. These modules are produced in a body shop which requires welding stations which are closely placed thanks to the smaller size of the modules and commonality of parts and sub assemblies. A stainless steel bulk head is provided on the adjoining faces of each of the two modules. Similarly, stainless steel male and female joining pieces are provided at the ends of the chassis frame on each of the modules. Both front and rear bulkheads are welded to front and rear modules in a electro mechanical shuttle and electro pneumatic fixture having X, Y, Z linear motion system for precise alignment. These are matched and numbered so that the same combinations of modules are assembled together after the modules are electro coated.
The modules are transported to the paint shop on a conveyor systems used for other vehicles which are of much smaller in size. These modules are subjected to sixth generation cathodic electro deposition (CED) rust prevention process which ensures highest level of surface protection. The challenge of accommodating the entire buss shell in the CED tank is overcome by making the shell in two modules which are CED coated separately and later joined to make the full shell.
After the modules are CED coated, they are brought together on a electro pneumatic fixture having X, Y, Z linear motion system for precise alignment and then bolted together. They are joined together in aligned and bolted condition by MIG argo shield

welding with stainless steel filler between the stainless steel bulkheads and male and female joining pieces on chassis ends of each module. Additional stainless steel reinforcement is welded at the joint of the chassis to ensure stiffness of chassis. The design ensures that all welding after the CED coat of the modules is performed on parts made of stainless steel. As the final joining is done on stainless steel parts with stainless steel filler, corrosion protection is guaranteed. This method has been tested and proved for 1000 Hours of salt spray life for the components.
After the modules are joined together, the shell is taken up for pasting of stainless steel stretch panels, plastic front and rear fascia and finish painting.
The above method of making a long bus body shell results in a much lighter body shell produced in a comparatively smaller welding line and smaller and cheaper CED tank and automation system. Heavy investments on large plants and conveyor systems are saved without any compromise on the structural stiffness and corrosion resistance of the body shell.

WE CLAIM:
1. A bus body shell which is fabricated from stamped sheet metal parts, in two or more modules , individually CED coated and connected together to form an integral one piece structure; wherein .
stainless steel bulk heads attached to the ends of bus modules which are connected to each other by MIG argo shield welding with stainless steel filler after the bus modules are individually electrcoated;
wherein the joining the chassis frames of a monocoque bus shell by using male and female stainless steel end connections which are connected by MIG argo shield welding with stainless steel filler.